Head and neck squamous cell carcinoma (HNSCC) is the fifth most common malignancy worldwide, representing a maj or international health problem. These tumors constitute an anatomically heterogeneous group of neoplasms arising from the oral cavity, oropharyrax, hypopharynx, larynx and nasopharynx. While all have in common an etiological association with tobacco and/or alcohol exposure, tumors originating from these different locations can exhibit varying behavior that is not predictable by histopathology of the primary tumor but is diseemable by gene profiling. Thus, gene expression profiling of primary tumors using sophisticated eDNA microarray and global proteomic analyses will likely yield information that will predict aggressive growth, metastatic potential and responsiveness to several types of therapy. The long-term goal of the proposed study is to use proteomic analysis of primary HNSCC to identify proteins that will differentiate tumor types and be used to predict tumor behavior. While surgery can cure early stage disease, multimodality therapy is of limited success in later stage HNSCC. Thus new diagnostics that can predict tumor behavior including response to therapy will have high clinical impact. Our goal in the proposed study is to identify specific changes in the proteome that predict tumor behavior and patient outcome in HNSCC, and to develop new, simple diagnostic tests that will enhance patient care and improve clinical outcome. The specific aims for the R21 feasibility phase are: 1- Test the reliability of protein extraction and of LC-MS analysis. Using a random effects model, reliability and standard error of measurement will be computed and the criterion for proceeding is reliability with lower confidence bound of>90%. 2- Test the feasibility that LC-MS analysis can be used to discrirm'nate/classify HNSCC with different clinical status. Target peptides with a reliability score cutoff from aim 1 will be used in standard statistical discrimination analysis and supervised clustering of the data to identify either single targets or groups of target pcptides than can discriminate samples with various clinical correlates of survival, such as stage, recurrence, and metastatic potential. The specific aims for the R33 phase will: -1- expand global proteomic and clinical data collection with analysis of HNSCC from three anatomic sites yielding a total of 135 samples;2- identify and characterize peptides that discriminate biologic variability;and 3- initiate development of new diagnostic tests.